It is known that vulcanized rubber compositions generally suffer so-called blooming, in which vulcanization accelerators, etc. migrate to the surfaces and deposit thereon with the lapse of time, so that the appearance of the vulcanized rubber compositions deteriorates.
A known method for inhibiting such blooming is to incorporate a non-reactive phenol-formaldehyde resin or polyethylene glyco) (see JP-B-59-15345). (The term "JP-B" as used herein means an "examined Japanese patent publication".)
Although this conventional technique is effective in retarding the progress of blooming to some degree, it has been ineffective in preventing the occurrence of blooming over a sufficiently long period of time.
On the other hand, as a technique for imparting electrical conductivity and antistatic performance to vulcanized rubbers, incorporation of carbon black or a metal powder into rubbers in known.
However, use of carbon black has had a problem that since the resulting rubber inevitably assumes a black color, it cannot be used in applications requiring tints other than black, for example, such applications as a paper-feed belt or roller which is strictly required not to cause black fouling. Further, use of a metal powder has been defective in that the resulting rubber has a reduced tensile strength and an increased specific gravity.